Electrical contact element for receiving a male pin



April '24, 1956 MARTINES 2,743,428

ELECTRICAL CONTACT ELEMENT FOR RECEIVING A MALE FIN Filed Nov. 8, 1954INVENTOR.

- R 49119 Marzjnes ATTORNEYS United States Patent ELECTRICAL CONTACTELEMENT FOR RECEIVING A MALE PIN This invention relates to improvementsin an electric plug, particularly the electric contact elements forplugs used for connecting and disconnecting electric heating devicesand/or the like with a source of electricity.

An electric contact element of the above character in common use in thetrade is formed of a single length of suitable material concave in crosssection at both ends and bent back upon itself at the midpoint toprovide a pair of resilient jaws. The jaws are made to converge towardsthe free end thereof to form a restricted opening thereto in an attemptto provide the necessary frictional engagement with the round terminalcontact pin received between the jaws. A disadvantage of this generaltype of contact element is that the engagement between the terminal pinand the jaws is had only at line contact crosswise of the jaws. Thispermits a lateral shifting and wiggling action between the jaws and theterminal pin which is objectionable.

An object of the invention is to provide a contact element of the abovecharacter which is so constructed as to overcome the disadvantagesheretofore mentioned.

A more specific object of the invention is to provide a contact elementwhich is so constructed as to provide a positive contact with theterminal pin at many spaced transverse cross sections of the contactelement.

Another object is to provide a contact element in which there will be afour point contact engagement with the terminal pin at any giventransverse cross section of the contact element.

Another object is to provide a contact element which will, underpressure of the engagement of the terminal pin, yield along a lineextending parallel to the axis of the terminal pin.

With these and other objects in view, the invention consists of certainnovel features of construction as will be more fully described andparticularly pointed out in the appended claims.

In the accompanying drawings:

Figure 1 is a plan view of a connector plug with one half thereofremoved and showing the electric contact elements embodying myinvention;

Figure 2 is a plan view on a larger scale of one of the contact elementsshown in Figure 1;

Figure 3 is a similar view of the opposite side of the contact element;

Figure 4 is an edge view of the contact element; and

Figure 5 is a sectional view taken substantially along line 5-5 ofFigure 1 and showing a terminal pin of an electrical appliance engagedwith the contact element.

The connecting plug shown is of conventional design comprising aninsulating casing preferably made of two similar parts 11, only one ofwhich is shown. The parts 11 are held together as by means of screws 12passing through the central wall portion 13 and engaged by clamp nuts14. The casing has spaced longitudinal recesses 15 which extend inwardlyfrom one end of the casing to a common cavity 17, bore 16 extendinginwardly from the other end of the casing into the cavity.

I 2,743,428 Patented Apr. 24, 1956 The cable or electric cord 18 passesthrough the bore 16 into the cavity 17 and. branches therefrom torecesses 15 to be attached. to the contacting elements 20 which arereceived and held in position by engagement between adjacent wallportions of the casing as will here inafter appear.

According to the present invention the contact element 20 is made from asingle strip of suitable flat sheet resilient electrical conductingmaterial which is subjected to a sequence of severing, stamping, andbending operations to form a socket portion 21 which is joined by a flatshank 22 to a pair of arms 23 which. are adapted to be bent and crimpedabout the wire of the cord 18 received between the arms. The socketportion 21 is generally circular in cross section but out of round withreference to the axis thereof as will hereinafter appear. Between theoppositely disposed longitudinai ribs 24 which extend from adjacent thefree end of the socket to adjacent the shank 22 on a plane generallycontiguous to the plane of shank 22 there is an arcuate wall portion 25.This wall portion is formed on a radius which is smaller than the radiusof the terminal contact pin P to be received in electrical engagementtherewith. Because of the dilference in radii. two spaced longitudinalcontact areas will result (see Figure 5). The arcuate wall portions 26of the socket extending from the ribs 24 are formed on a radius greaterthan the radius of pin P and are provided with reinforcing ribs 27.These wall portions are free of the shank 22and have an inherentresiliency along the axial extent of rib 24 to give a hinging springaction. The edges 28 of the portions 26 are spaced from each other asubstantial distance and are turned inwardly to provide two longitudinalareas of contact 26'. The edges 28 also, by virtue of their springaction, maintain the pin P in firm contact with the points of contact inthe portion 25. Thus, four longitudinal points of contact are securedbetween the walls of the socket and the terminal pin P received thereinas well as a firm embracing relationship therebetween. This em bracingrelationship, it will be noted, is enhanced by the long hinging linealong arcuate rib 24 which reduces the chance of fatigue under repeatedbending, the stress on the material being distributed in two senses.

The socket walls are made straight in the longitudinal direction, andthe wall portions 26 are resilient, yielding outwardly at the junctionthereof with the ribs 24. In order to enhance this resiliency, the wallportions 26 are separated from the wall 25 in a longitudinal directionas by means of a slot 29 (see Figure 4). Wall portions 25 and 26 areflared at the entrance end of the socket as at 30 to facilitate theentering of the terminal contact pin P. The shank 22 extends beyond thesides of the socket and provides tabs 31 to engage in recesses 32, 33formed in the walls of the casing so as to be held in position by thewalls thereof.

From the above description it will be apparent that the socket is madewith a slightly smaller interior diameter than thcdiameter of theterminal contact pin P so that the bore of the socket 21 will engage atfour points at any given transverse cross section thereof. It will befurther apparent that the tension of the walls 26 exerted on theterminal contact pin P will tend to move the pin into further engagementwith the points of engagement with wall 25. This in turn tends to causea spreading of said wall 25 and thus places said wall under tension tofurther increase the grip of the socket walls on the said pin P andprovide for a good electrical engagement between contacts.

I claim:

1. In an electric attachment plug, a contact element for receiving amale pin formed from one piece of resilient electrical conductingmaterial bent to form a straight socket with a wire connecting shank,said socket having in cross section an out of round wall with two spacedlongitudinal edges removed from said shank and resiliently yieldablealong a line substantially parallel to the longitudinal axis of thesocket, the bottom half of said wall being formed on a first radius andthe top half of said wall being formed on a second radius whose centeris above the center of the first, said wall having four longitudinalspaced points of engagement crosswise thereof equal distances from theaxis of said socket whereby a round terminal contact received in saidsocket will engage at four points at many transverse cross sections ofthe contact.

2. A one piece contact member for attachment to a plug comprising asubstantially tubular body adapted to receive a cylindrical contact pin,said body being open at one side longitudinally of the body and providedwith opposite outer ribs extending lengthwise of the body, said bodyhaving a wall portion between said ribs extending crosswise on an arc ofa first radius having a center midway of said ribs, said wall portionhaving a wire connecting shank extending therefrom, and resilient wallper tions extending from said ribs toward each other on a curvature witha second radius having a center midway of said ribs and further removedfrom said wall portion than the center of said first radius to providewith the said first wall a four point contact engagement with a contactpin at many transverse cross sections through said body, said resilientwall portion free of said shank and yielding along a line extendingparallel and adjacent said ribs.

References Cited in the file of this patent UNITED STATES PATENTS1,649,305 Hartmann Nov. 15, 1927 1,921,745 Grace Aug. 8, 1933 2,086,522Bergstrom July 13, 1937 2,151,226 Ogle Mar. 21, 1939 2,453,826 AdamsNov. 16, 1948 FOREIGN PATENTS 564,889 Germany Nov. 24, 1932 758,099France Oct. 23, 1933

